Resizing canvas only works in one direction

I try to fit threejs into an application that fills the whole screen:

Resizing works from big to small. But not from small to big, After reszizinfg from small to big I get scroll bars. After some debugging I noticed that I get way to high values for the clientHeight in my windowResizeHandler. But I don’t know how to solve it.

At first load and after refreshing the dimension are right. Also If I make an application without threejs, I have no problems:
So I guess its an issue with threejs I have